Filter unit and filtrate collector therefor

ABSTRACT

A filter unit generally including a tank having a restricted opening into which a fluid distributor may be fitted, a return conduit disposed within the fluid tank and connected to the distributor, at least one filtrate collector disposed in the tank, including a housing defining a fluid chamber communicating with the return conduit and a plurality of filtrate collector conduits operatively connected to the housing for pivotal movement in planes including a longitudinal center line of the housing whereby the collector units may be moved together to positions adjacent the housing center line to permit the insertion or removal of the filtrate collector through the restricted opening of the tank and spread apart to positions disposed substantially radially relative to the housing center line, within the tank, and a filter medium disposed in the fluid tank embedding the collector conduits.

United States Patent 1 Barrera [111 3,747,768 [4s] July 24, 1913 [75]lnventor:

[73] Assignee: Wilkes Pool Corporation, Berwick,

[22] I Filed: May 9, 1972 [21] Appl. No.: 251,760

Salvatore E. Barrera, Berwick, Pa.

[52] 11.8. CI. 210/288, 210/289 [51] Int. Cl 3016 29/08 [58] Field ofSearch 138/177, 178, DIG. 11;

Primary Examiner-Samih N. Zaharna Assistant Examinerlvars Cintins W H Attorney-Thomas B. Van Poole, Peter N. Lalos et al.

[57] ABSTRACT A filter unit generally including a tank having arestricted opening into which a fluid distributor may be fitted, areturn conduit disposed within the fluid tank and connected to thedistributor, at least one filtrate collector disposed in the tank,including a housing defining a fluid chamber communicating with thereturn conduit and a plurality of filtrate collector conduitsoperatively connected to the housing for pivotal movement in planesincluding a longitudinal center line of the housing whereby thecollector units may be moved together to positions adjacent the housingcenter line to permit the insertion or removal of the filtrate collectorthrough the restricted opening of the tank and spread apart to positionsdisposed substantially radially the collector conduits.

16 Claims, 8 Drawing Figures Pmmmm 3,147, 768

SHEET 1 0F 3 PATENTIED 3. 747. 768

SHEEI 3 BF 3 FILTER UNIT AND FILTRATE COLLECTOR THEREFOR This inventionrelates to a filter unit and more particularly to a novel unit forfiltering liquids such as water used in swimming pools. The inventionfurther contemplates a novel filtrate collector for a filter unit,particularly adapted for use in filter units utilizing sand as a filtermedium.

In most conventional units used for filtering liquids, there usually isprovided a fluid tank having a restricted opening, a fluid valve mountedin the opening, a return line disposed within the fluid tank andconnected to the valve in the opening, and a filter element or mediumthrough which the liquid to be filtered is passed during the filteringoperation. In applications where a filter medium such as sand is used,it has been a common practice to provide an elongated return conduit inthe fluid tank provided with a plurality rigidly secured, radiallyprojecting conduits having filtrate receiving openings, which areembedded in the sand and function to receive filtrate through theopenings and conduct such filtrate to the return conduit from where itis conducted to the fluid valve in the opening of the tank.

In the fabrication of such types of units, due to the construction ofthe filtrate collectors and the restricted access openings of the tanks,it has been necessary to secure the filtrate collectors to the returnconduit of the filter, within the filter tank. Such procedure has beenfound to be undesirable in that it is cumbersome and time consuming.

Accordingly, it is the principal object of the present invention toprovide an improved filter unit.

Another object of the present invention is to provide a novel unit forfiltering liquids.

A further object of the present invention is to provide a novel filterunit utilizing sand as a filter medium.

A still further object of the present invention is to provide animproved filter unit having a novel filtrate collector.

Another object of the present invention is to provide an improved filterunit which is provided with a preassembled filtrate collector that canbe readily inserted into and removed from the fluid tank thereof.

A further object of the present invention is to provide an improvedfilter unit utilizing sand as a filter medium disposed within a fluidtank provided with a restricted access opening, having a novel filtratecollector adapted to be embedded in the sand medium and readilyinsertable and removable through the restricted access opening.

Another object of the present invention is to provide a novel filtratecollector for a filter unit.

A further object of the present invention is to provide a novel filtratecollector for a filter unit, which may be preassembled for mounting inthe tank of the filter unit.

A still further object of the present invention is to provide a novelfiltrate collector suitable for use in a filter unit provided with afluid tank having a restricted access opening, which may be readilyinserted and removed through such restricted access opening.

Another object of the present invention is to provide a novel filtratecollector adapted to be embedded in a filter medium disposed in the tankof a filter unit.

A further object of the present invention is to provide a novel filtratecollector adapted to be embedded in a filter medium of sand depositedinthe tank of a filter unit.

A still further object of the present invention is to provide a novelfilter unit and a novel filtrate collector for a filter unit, each ofwhich are comparatively simple in construction, relatively inexpensiveto manufacture and highly effective in performance.

Another object of the invention is to provide a novel method of making afiltrate collector.

Other objects and advantages of the present invention will become moreapparent to those persons having ordinary skill in the art to which theinvention pertains, from the following description taken in conjunctionwith the accompanying drawings wherein:

FIG. 1 is a perspective view of an embodiment of the invention;

FIG. 2 is a perspective view of a filtrate collector utilized in theembodiment shown in FIG. 1, illustrating the components thereof inexploded relation;

FIG. 3 is an enlarged, vertical cross-sectional viewof the embodimentillustrated in FIG. I, having portions thereof broken away;

FIG. 4 is a cross-sectional view taken along line 4-4 in FIG. 3;

FIG. 5 is an enlarged cross-sectional view taken along line 5-5 in FIG.4;

FIG. 6 is an enlarged cross-sectional view taken along line 6-6 in FIG.5;

FIG. 7 is a vertical cross-sectional view of the embodiment shown inFIG. 1, illustrating the manner in which the filtrate collector may becollapsed so that it may be inserted or removed through the restrictedaccess opening of the tank thereof; and

FIG. 8 is a vertical cross-sectional view of another embodiment of theinvention utilizing a number of filtrste collectors embedded in thefilter medium disposed within the tank thereof.

Briefly described, the present invention relates to a filter unitgenerally including a fluid tank having a restricted opening in theupper end thereof in which a fluid distributor provided with at leasttwo fluid ports may befitted, a return conduit disposed within the fluidtank, communicating at an upper end thereof with a port of the fluiddistributor, a filter medium disposed in the fluid tank, and at leastone filtrate collector disposed within the tank embedded in the filtermedium and communicable with the return conduit. The collector filtrateincludes a housing defining a fluid chamber communicating with thereturn conduit, and a plurality of filtrate collector conduitsoperatively connected to the housing for pivotal movement in planesincluding a longitudinal center line of the housing whereby thecollector conduits may be moved together to positions adjacent thehousing center line to permit the insertion or removal of the filtratecollector through the restricted opening in the tank, and spread apartto positions disposed substantially radially relative to the housingcenter line within the tank. Each of the collector conduits is providedwith a longitudinally disposed fluid passageway communicable with thefluid chamber of the collector housing when the collector conduits aredisposed in their spread-apart positions, and a plurality of filtratereceiving openings intercommunicating the exterior thereof with thelongitudinal passageway in the conduit.

Referring to FiG. 1, there is illustrated a filter system 10 consistingof a filter unit 11 a selector valve 12 mounted on the filter unit, apump 13 driven by a motor 14, an inlet line 15 interconnecting the bodyof liquid to be filtered and the inlet side of the pump 13 and providedwith a cutoff valve 16 and chlorinator 17, a fluid line 18interconnecting the pump 13 and the selector valve 12 and a fluid outletline 19 interconnecting the selector valve 12 and the body of liquidbeing filtered. As best illustrated in FIG. 3, the filter unit 11consists of a tank 20, a filter medium 21 disposed in the tank, afiltrate collector 22 disposed within the tank and embedded in thefilter medium, and a return conduit 23 disposed within the tank, havingthe lower portion thereof embedded in the filtrate medium and the lowerend thereof communicating with the filtrate collector 22.

The filter tank generally consists of a bottom wall section 24 having anupwardly curved peripheral portion, seated on an annular base member 25,a substantially cylindrical side wall section 26, and an upper wallsection 27 having a downwardly curved peripheral portion and an axiallydisposed restricted access opening 28 which is threaded. As bestillustrated in FIG. 3, the selector valve 12 is mounted on the filterunit 11 by means of an adapter 29 which is threaded into the restrictedaccess opening 28. The construction and operation of the selector valve12 and adapter 29 are described in my co-pending U.S. Pat. application,Ser. No. 220,834, filed Jan. 26, 1972. As indicated in such description,the adapter 29 is provided with an axially disposed opening 30 and aplurality of circumferentially spaced ports 31 which communicate withthe interior of the tank 20.

Within the tank 20, the return conduit 23 is mounted axially,communicates at its upper end with the opening 30 of adapter 29 andterminates at its lower end above the lower wall section 24 of the tank.As shown in FIG. 3, the lower portion of conduit 23 is embedded in thefiltering medium 21. Also embedded in the medium and disposed betweenthe lower end of the return conduit 23 and the bottom wall section 24 ofthe tank is the filtrate collector 22. As best seen in FIGS. 2 through5, the filtrate collector consists of a center housing 33 defining afluid chamber 34, and a plurality of filtrate collector conduits 35. Thehousing 33 includes a lower housing section 36 adapted to be seated onthe bottom wall section 24 of the tank and an upper housing section 37adapted to be connected to the lower end of the return conduit.

The lower housing section 36 consists of a circular bottom wall portion38 provided with an opening 380 communicating with a depending conduitportion 39. The conduit portion 39 is adapted to be seated in a recess40 provided in a plug 41 threaded into an axially disposed opening 42 inthe bottom wall section 24 of the tank. The section 36 further consistsof an upwardly projecting annular flange portion 43 defining the lowerportion of fluid chamber 34, providing an annular seating surface 44 asbest illustrated in FIG. 2. The upper housing section 37 is providedwith an upper circular wall portion 45 having an opening 46, an upwardlyprojecting, annular flange portion 47 adapted to receive the lower endof the return conduit 23 to communicate the fluid chamber 34 with thereturn conduit through the opening 46, and a depending, annular flangeportion 48 defining the upper portion of fluid chamber 34 when the lowerannular surface 49 thereof is seated on the annular surface 44 of lowerhousing section 36 and the housing sections are secured together bymeans of a plurality of circumferentially spaced screws 50.

As best seen in FIGS. 2 and 5, the annular surface 44 of lower housingsection 36 is provided with a plurality of circumferentially spacedrecesses 51 which extend radially and through the annular flange portion43, and the annular surface 49 of upper housing section 37 is providedwitha plurality of circumferentially spaced, complementary recesses 52which also are radially disposed and extend through the flange portion48, and are adapted to register with the recesses 51 when the housingsections are joined together to provide the housing 33 defining thefluid chamber 34. The recesses 51 and 52 have spherical configurationsso that when the housing sections 36 and 37 are joined together to formthe housing 33, the housing will be provided with a plurality ofcircumferentially spaced spherical sockets 53 inter-communicating thefluid chamber 34 with the exterior of the housing 33.

Referring to FIGS. 2, 5 and 6, each of the filtrate collector conduits35 consists of a base connecting member 54 and a perforated member 55.The base connecting member 54 has a tubular configuration providing anelongated passageway 56. It further is provided with an inner,spherically configured end portion 57 seated in a spherical socket 53 inhousing 33 to provide a ball and socket connection between the filtratecollector and the center housing, with the passageway 56 adapted tocommunicate with the fluid chamber 34, and a reduced, outer end portion58 which is received within an inner end of the perforated member 55.The perforated member 55 includes an elongated cylindrical section 59defining a longitudinally disposed fluid passageway 590, an inner wall60 provided with an opening for receiving the reduced outer end portion58 of the base connecting member 54 therethrough to intercommunicate thefluid passageways 56 and 59a, and an outer end wall section 61. Thecylindrical section 59 is internally splined as shown in FIG. 6 toprovide a plurality of longitudinally disposed, circumferentially spacedinternal splines or grooves 62, and further is provided with a pluralityof longitudinally spaced, circumferentially disposed grooves 62 in. thecylindrical outer surface thereof, each having a depth sufficient tocommunicate such circumferentially disposed grooves with thelongitudinally disposed grooves 62 to provide a plurality oflongitudinally spaced sets of circumferentially spaced openings 64intercommunicating the longitudinally disposed fluid passageway 59a ofthe filtrate collector and the exterior thereof. It is contemplated thatthe filtrate receiving openings 64 of the filtrate collector be providedwith a size smaller than the grain size of the filter medium in whichthe filtrate collector will be embedded during normal operatingconditions. It will be appreciated that the size of such openings can bedetermined by the widths of longitudinal grooves 62 or circumferentialgrooves 63. t

It is contemplated that the perforated members 55 of the filtratecollector conduits shall be constructed from any suitable material whichis incapable of physically or chemically reacting with the liquid to befiltered or any of the materials contained within such liquid. Itfurther is contemplated that such perforated members will be fabricatedby utilizing tubular stock of a suitable material such as a plastic,forming the internal splines 62 and then forming the cylindrical grooves63 to a depth sufficient to communicate the grooves 63 with the grooves62. The size of the openings can be fixed by selecting appropriatewidths for one or both of the grooves 62 and 63. The splines 62 can beformed either by an extrusion process or by taking tubular stock andmachining the splines into it, and the recesses 63 can be formed by anyconventional cutting method.

In assembling the filtrate collector 22, the filtrate collector conduits35 are first preassembled by press fitting the base connecting members54 into the openings provided in the inner end wall sections 60 of theperforated members 55. The filtrate collector conduits 36 are thenconnected to the housing 33 by seating the spherical end portions 57 ofthe conduits 35 in the spherically configured recesses 51 of lowerhousing sections 36, positioning the upper housing section 37 on thelower housing section 36 so that the surface 49 is seated on the surface44, and the spherically configured recesses 52 are seated on thespherically configured portions 57, and then securing the housingsections together by means of the screws 50. The filtrate.

collector conduits 35 will then be disposed substantially radiallyrelative to the axial center line of the housing 33, and be connectedthereto by means of ball and socket connections, with their alignedpassageways 56 and 59a communicating with the filter chamber 34.

When it is desired to assemble the filter unit 11, the return conduit 23is fitted into the annular flange portion 47 of housing 33, the filtratecollector conduits 35 are pivoted upwardly and inwardly toward thereturn conduit, and the entire assembly is inserted through the threadedopening 28 of the tank, as illustrated in FIG. 7. in this regard, it isto be noted that the cylindrical outer wall of the upper housing section37 is provided with a plurality of circumferentially spaced recesses 65which are adapted to receive the intermediate portions of baseconnecting members 54 of the filtrate collector conduits, and thuspermit the filtrate collector to be collapsed similar to an umbrella.After the filtrate collector has been inserted through the opening 28 inthe tank, the center housing thereof is positioned within the tank byseating the conduit portion 39 thereof in the recess 40 provided in thethreaded plug 41. The assembler may then reach through the opening 28and spread the conduits 35 apart into positions as illustrated in FIG.3. The filter medium, usually sand, is then poured into the tank throughaccess opening 28 so that the filtrate collector and lower portion ofthe return conduit become embedded in the medium with the return conduitdisposed axially, and a certain amount of head space is provided in thetank. The valve 12 with the adapter 29 depending therefrom is thenfitted on the tank by threading the adapter into the access opening 28so that the axially disposed opening in the adapter communicates withthe upper end of the return conduit and the circumferentially spacedports 31 communicate with the head space above the filter medium in thetank. The filter system then can be completed by securing the fluid line18 to the valve 12, interconnecting the inlet line with the body offluid to be filtered and interconnecting the discharge line 19 with these- 'lec tor valve 12 and the body of fluid.

the filter medium 21 where the filtering action occurs. The filtratewill then flow through filtrate receiving openings 64 and passageways59a and 56 of the filtrate collector conduits 35, fluid chamber 34 inhousing 33, return conduit 23, selector valve 12 and then discharge line19 to the body of liquid. Whenever it is desired to backflush the filterunit, the selector valve 12 is reset to its proper position so that theflow of liquid through the filter unit is reversed. Under suchconditions, liquid under pressure will flow through opening 30 of theadapter, return conduit 23, fluid chamber 34 of housing 33, alignedpassageways 56 and 59a, and openings 64 in the filtrate collectorconduits 35, upwardly through the filter medium 21 and then throughports 31 in the adapter to be discharged through the selector valve 12.The various positions of the selector valve 12 to provide the differentdirections of flow of liquid through the filter unit 11 and selectorvalve 12 are described in detail in my co-pending US. Pat. application,Ser. No. 220,834, as aforementioned.

To disassemble the filter unit 11 for maintenance purposes or perhaps toreplace the filtrate collector 22, the selector valve 12 with theadapter 29 is first removed from the tank. The filter medium 21 is thenremoved until the filtrate collector is freed and can be lifted out ofthe tank. T0 permit the filtrate collector to pass through the accessopening 28, the filtrate collector conduits 35 are pivoted inwardlyagainst the return conduit, and then lifted upwardly and removed throughthe opening 28. It is to be noted that the'tank 20 may be drained simplyby removing the threaded plug 41 from the bottom wall section 24.

Referring to FIG. 8, there is illustrated another em- I bodiment of theinvention. This embodiment is similarv to the embodiment illustrated inFIGS. 1 through 7 with the exception that a plurality of filtratecollectors 22 are utilized which are interconnected by one or morereturn conduit sections 23a and are connected to the adapter 29 by meansof a return conduit section 23b. It will be appreciated that the centerhousing 33 interposed between a pair of return conduit sections will bemodified slightly by providing an opening in the lower wall thereofwhich communicates with a return conduit section. The number of filtratecollectors 22 utilized in a filter unit will depend upon the size andcapacity of a unit. It will be seen, however, that the use of a numberof filtrate collectors 22 will function to increase the capacity of afilter unit.

Although any suitable type of filter medium may be utilized in thefilter unit 11, it is contemplated that any conventional high ratefilter sand can be used. Regardless of the type of filter medium used,it further is contemplated that the filtrate receiving openings 64 ofthe filtrate collector conduits 35 will be of a size smaller than thegrains of the filter medium. j p

From the foregoing detailed description, it will be evident that thereare a number of. changes, adaptations and modifications of the presentinvention which come within the province of those persons skilled in theart. However, it is intended that all such variations not departing fromthe spirit of the inventin be considered as within the scope thereof aslimited solely by the appendant claims.

I claim:

1. A filter unit comprising a fluid tank having a restricted opening inan upper end thereof into which a fluid distributor provided with atleast two fluid ports may be fitted, a return conduit disposed withinsaid fluid tank, said return conduit communicating at an upper endthereof with a port of said fluid distributor, at least one filtratecollector disposed in said tank, said filtrate collector including ahousing defining a fluid chamber communicating with the interior of saidreturn conduit, and a plurality of filtrate collector conduitsoperatively connected to said housing for pivotal movement in planesincluding a longitudinal center line of said housing whereby saidcollector conduits may be moved together to positions adjacent saidcenter line to permit the insertion or removal of said filtratecollector through the restricted opening of said tank, and spread apartto positions disposed substantially radially relative to said centerline within said tank, each of said collector conduits having alongitudinally disposed fluid passageway communicable with the fluidchamber of said collector housing when said collector conduits aredisposed in their spread-apart positions, and a plurality of filtratereceiving openings intercommunicating the exterior thereof with saidlongitudinal passageway, and a filter medium disposed in said fluid tankembedding said collector conduits.

2. A filter unit according to claim 1 wherein said filtrate collectorconduits are pivotally connected to said housing with ball and jointconnections.

3. A filter unit according to claim 1 wherein said filtrate receivingopenings comprise a plurality of longitudinally spaced sets ofcircumferentially spaced openings.

4. A filter unit according to claim 1 wherein each of said filtratecollector conduits includes a section provided with an internallysplined configuration and a plurality of longitudinally spaced,circumferentially disposed grooves communicating with the longitudinalgrooves of said internal splines to provide said filtrate receivingopenings.

5. A filter unit according to claim 1 wherein said filter mediumconsists of sand and the size of said filtrate receiving openings issmaller than the grain size of the sand.

6. A filter unit according to claim 1 wherein the housing of onefiltrate collector includes means for seating the filtrate collector ona bottom wall of said fluid tank.

7. A filter unit according to claim 1 including a plurality of filtratecollectors interconnected by segments of said return conduit.

8. A filter unit according to claim 1 wherein said filtrate collectorhousing comprises a lower section including a circular bottom wallportion and an upwardly projecting annular flange portion defining alower portion of said housing chamber, an upper sectionincluding acircular upper wall portion and a depending annular flange seated on theannular flange portion of said lower section and defining an upperportion of said 7 housing chamber, and means for securing said housingsections together, at least one of the circular wall portions of saidhousing sections having an opening intercommunicating said housingchamber and said return conduit, the annular flange portions of saidhousing sections having a plurality of openings intercommunicating theexterior thereof and the fluid chamber of said housing, having aspherical configuration, the outer wall of said upper housing sectionhaving a plurality of circumferentially spaced, longitudinally disposedrecesses aligned with said openings having spherical configurations, andsaid filtrate collector conduits having ball portions seated in saidopenings having spherical configurations to provide ball and socketconnections between the collector conduits and said housing and adjacentlongitudinally disposed sections receivable within the recesses in thewall of said upper housing section when said collector conduits aremoved together by pivoting them into positions adjacent the longitudinalcenter line of said housing.

9. A filtrate collector for a filter unit including a filter tank havingan opening into which a fluid distributor provided with at least twofluid ports may be fitted, and a return conduit disposed within saidfluid tank communicating at an end thereof with a port of said fluiddistributor, comprising the housing including a fluid chamber providedwith at least one opening communicable with said return conduit, and aplurality of filtrate collector units operatively connected to saidhousing for pivotal movement in planes including a longitudinal centerline of said housing whereby said collector units may be moved togetherto positions adjacent said center line to permit the insertion orremoval of said filtrate collector through the opening of said tank, andspread apart to positions disposed substantially radially relative tothe center line of said housing, each of said collector units having alongitudinally disposed fluid passageway communicable with the fluidchamber of said collector housing when said collector units are disposedin their spread-apart positions, and a plurality of filtrate receivingopenings intercommunicating the exterior thereof and said longitudinalpassageway.

10. A filtrate collector according to claim 9 wherein said filtratecollector conduits are pivotally connected to said housing with ball andjoint connections.

11. A filtrate collector according to claim 9 wherein said filtratereceiving openings comprise a plurality of longitudinally spaced sets ofcircumferentially spaced openings.

12. A filtrate collector according to claim 9 wherein each of saidfiltrate collector conduits includes a section provided with aninternally splined configuration and a plurality of longitudinallyspaced, circumferentially disposed grooves communicating with thelongitudinal grooves of said internal splines to provide said filtratereceiving openings.

13. A filtrate collector according to claim 9 wherein the size of saidfiltrate receiving openings is smaller than the size of sand used as afilter medium in said tank.

14. A filtrate collector according to claim 9 wherein the housing ofsaid filtrate collector includes means for seating the filtratecollector on a bottom wall of said fluid tank.

15. A filtrate collector according to claim 9 wherein said housingincludes a pair of openings communicable with segments of said returnconduit.

16. A filtrate collector according to claim 9 wherein said housingcomprises a lower section including a circular bottom wall portion andan upwardly projecting annular flange portion defining a lower portionof said housing chamber, an upper section including a circular upperwall portion and a depending annular flange seated on the annular flangeportion of said lower section and defining an upper portion of saidhousing chamber, and means for securing said housing sections together,at least one of the circular wall portions of said housing sectionshaving an opening for communicatingthe housing chamber with said returnconduit,

the annular flange portions of said housing sections having a pluralityof openings intercommunicating the exterior thereof and the fluidchamber of the housing, having spherical configurations definingsockets, the outer wall of said upper housing section having a pluralityof circumferentially spaced, longitudinally dis-i posed recesses alignedwith said openings having spherical configurations defining sockets, andsaid filtrate collector conduits having ball portions seated in said

1. A filter unit comprising a fluid tank having a restricted opening inan upper end thereof into which a fluid distributor provided with atleast two fluid ports may be fitted, a return conduit disposed withinsaid fluid tank, said return conduit communicating at an upper endthereof with a port of said fluid distributor, at least one filtratecollector disposed in said tank, said filtrate collector including ahousing defining a fluid chamber communicating with the interior of saidreturn conduit, and a plurality of filtrate collector conduitsoperatively connected to said housing for pivotal movement in planesincluding a longitudinal center line of said housing whereby saidcollector conduits may be moved together to positions adjacent saidcenter line to permit the insertion or removal of said filtratecollector through the restricted opening of said tank, and spread apartto positions disposed substantially radially relative to said centerline within said tank, each of said collector conduits having alongitudinally disposed fluid passageway communicable with the fluidchamber of said collector housing when said collector conduits aredisposed in their spread-apart positions, and a plurality of filtratereceiving openings intercommunicating the exterior thereof with saidlongitudinal passageway, and a filter medium disposed in said fluid tankembedding said collector conduits.
 2. A filter unit according to claim 1wherein said filtrate collector conduits are pivotally connected to saidhousing with ball and joint connections.
 3. A filter unit according toclaim 1 wherein said filtrate receiving openings comprise a plurality oflongitudinally spaced sets of circumferenTially spaced openings.
 4. Afilter unit according to claim 1 wherein each of said filtrate collectorconduits includes a section provided with an internally splinedconfiguration and a plurality of longitudinally spaced,circumferentially disposed grooves communicating with the longitudinalgrooves of said internal splines to provide said filtrate receivingopenings.
 5. A filter unit according to claim 1 wherein said filtermedium consists of sand and the size of said filtrate receiving openingsis smaller than the grain size of the sand.
 6. A filter unit accordingto claim 1 wherein the housing of one filtrate collector includes meansfor seating the filtrate collector on a bottom wall of said fluid tank.7. A filter unit according to claim 1 including a plurality of filtratecollectors interconnected by segments of said return conduit.
 8. Afilter unit according to claim 1 wherein said filtrate collector housingcomprises a lower section including a circular bottom wall portion andan upwardly projecting annular flange portion defining a lower portionof said housing chamber, an upper section including a circular upperwall portion and a depending annular flange seated on the annular flangeportion of said lower section and defining an upper portion of saidhousing chamber, and means for securing said housing sections together,at least one of the circular wall portions of said housing sectionshaving an opening intercommunicating said housing chamber and saidreturn conduit, the annular flange portions of said housing sectionshaving a plurality of openings intercommunicating the exterior thereofand the fluid chamber of said housing, having a spherical configuration,the outer wall of said upper housing section having a plurality ofcircumferentially spaced, longitudinally disposed recesses aligned withsaid openings having spherical configurations, and said filtratecollector conduits having ball portions seated in said openings havingspherical configurations to provide ball and socket connections betweenthe collector conduits and said housing and adjacent longitudinallydisposed sections receivable within the recesses in the wall of saidupper housing section when said collector conduits are moved together bypivoting them into positions adjacent the longitudinal center line ofsaid housing.
 9. A filtrate collector for a filter unit including afilter tank having an opening into which a fluid distributor providedwith at least two fluid ports may be fitted, and a return conduitdisposed within said fluid tank communicating at an end thereof with aport of said fluid distributor, comprising the housing including a fluidchamber provided with at least one opening communicable with said returnconduit, and a plurality of filtrate collector units operativelyconnected to said housing for pivotal movement in planes including alongitudinal center line of said housing whereby said collector unitsmay be moved together to positions adjacent said center line to permitthe insertion or removal of said filtrate collector through the openingof said tank, and spread apart to positions disposed substantiallyradially relative to the center line of said housing, each of saidcollector units having a longitudinally disposed fluid passagewaycommunicable with the fluid chamber of said collector housing when saidcollector units are disposed in their spread-apart positions, and aplurality of filtrate receiving openings intercommunicating the exteriorthereof and said longitudinal passageway.
 10. A filtrate collectoraccording to claim 9 wherein said filtrate collector conduits arepivotally connected to said housing with ball and joint connections. 11.A filtrate collector according to claim 9 wherein said filtratereceiving openings comprise a plurality of longitudinally spaced sets ofcircumferentially spaced openings.
 12. A filtrate collector according toclaim 9 wherein each of said filtrate collector conduits includes asection provided with an internally Splined configuration and aplurality of longitudinally spaced, circumferentially disposed groovescommunicating with the longitudinal grooves of said internal splines toprovide said filtrate receiving openings.
 13. A filtrate collectoraccording to claim 9 wherein the size of said filtrate receivingopenings is smaller than the size of sand used as a filter medium insaid tank.
 14. A filtrate collector according to claim 9 wherein thehousing of said filtrate collector includes means for seating thefiltrate collector on a bottom wall of said fluid tank.
 15. A filtratecollector according to claim 9 wherein said housing includes a pair ofopenings communicable with segments of said return conduit.
 16. Afiltrate collector according to claim 9 wherein said housing comprises alower section including a circular bottom wall portion and an upwardlyprojecting annular flange portion defining a lower portion of saidhousing chamber, an upper section including a circular upper wallportion and a depending annular flange seated on the annular flangeportion of said lower section and defining an upper portion of saidhousing chamber, and means for securing said housing sections together,at least one of the circular wall portions of said housing sectionshaving an opening for communicating the housing chamber with said returnconduit, the annular flange portions of said housing sections having aplurality of openings intercommunicating the exterior thereof and thefluid chamber of the housing, having spherical configurations definingsockets, the outer wall of said upper housing section having a pluralityof circumferentially spaced, longitudinally disposed recesses alignedwith said openings having spherical configurations defining sockets, andsaid filtrate collector conduits having ball portions seated in saidopenings having spherical configurations defining sockets to provideball and socket connections between the collector conduits and saidhousing and adjacent longitudinally disposed sections receivable withinthe recess in the wall of said upper housing section when said collectorconduits are moved together by pivoting them into positions adjacent thelongitudinal center line of said housing.